A protease is a general term of an enzyme group that catalyzes hydrolysis of a peptide bond, and is widely distributed in microorganisms, animals and plants. Its application includes detergents for clothes, various detergents such as kitchen detergents, detergents for an automatic tableware washer and contact lens cleaners, toiletries such as bath products and keratolytics, food modifying agents for bread making, meat softening and marine product processing, digestion aids and antiinflammatory agents, and it has found wide acceptance in many fields.
It is a protease which is industrially mass-produced most among a large number of enzymes and has a great market scale. Among others, an alkaline protease for a detergent has played a significant role as an indispensable component in improvement of a washing power. As trade names of specifically marketed products as the alkaline protease, Sabinase, Cannase, Durazyme (manufactured by Novozyme), Makisakal (manufactured by Genencore), Blap (manufactured by Henkel) (all of them are registered trademarks), KAP (manufactured by Kao Corporation) are known.
These alkaline proteases for a detergent which have been used at present are derived from bacteria of the genus Bacillus, and belong to the subtilisin family classified in Class 1-S2 (refer to Non-patent Document 1). As true subtilisin, Subtilisin BPN′ and Carlsberg belonging to Class 1-S1, and the like are well known.
With respect to the protease for a detergent, an enzyme for a detergent having more improved properties has been explored. Enzymes having stability to heat and surfactants (refer to, for example, Patent Document 1), enzymes acting on an insoluble protein such as keratin and having high specific activity (refer to, for example, Patent Document 2), enzymes having excellent activity in a low temperature region (refer to, for example, Patent Documents 3 and 4), a method for improving stability to oxidizers (refer to, for example, Patent Document 5) and the like have been reported.
However, many of these enzymes are problematic respectively in reactivity under quite high alkaline conditions, Ca2+ ions-dependent thermostability, stability in concentrated surfactants or chelating agents and the like, and alkaline proteases so far discovered sometimes have not exhibited functions thereof satisfactorily.
Patent Document 1: Gazette of JP-A-6-70765
Patent Document 2: Gazette of JP-A-9-121855
Patent Document 3: Gazette of JP-A-5-211868
Patent Document 4: Gazette of JP-A-9-121856
Patent Document 5: Gazette of European Patent No. 0130756
Non-patent Document 1: Siezen et al., Protein Eng., 4, 719-737,